File Transfer

Blazor WASM, .NET5 I’m trying to transfer files to the server and back. I transmit parts of 3mb in the form of bytes. This consumes a lot of RAM by the browser. And when I transfer from the server, it happens very slowly for files larger than 3mb. Maybe there is a way to transfer a stream, not a byte? or maybe I have a failed approach?

proto

service Greeter {
  rpc UploadFile(stream FileRequest) returns (StatusRequest);
  rpc DownloadFile(FilesInfoRequest) returns (stream FileRequest)
}
message StatusRequest {
  string Status = 1;
}
message FileRequest {
    string FileName = 1;
    bytes FileBytes =2;
   
}
message FilesInfoRequest {
    string FileName = 1;
    string FilePath = 2;   
}

Sending method. Executed in the browser. Works fast. Google.Protobuf.UnsafeByteOperations.UnsafeWrap - consumes a lot of RAM ~ file 120mb - 1 gigabytes

private const int _maxSize = 3 * 1024 * 1024;
private byte[] _part = new byte[_maxSize];
private FileRequest _fileRequest;
private async void UploadFiles(InputFileChangeEventArgs e)
    {
      
        foreach (var file in e.GetMultipleFiles())
        {
            try
            {
                using var call = GreeterClient.UploadFile();
                using (var ms = file.OpenReadStream(file.Size))
                {
                   
                    while (ms.Length - ms.Position > 0)
                    {
                        if (ms.Length - ms.Position <= _maxSize)
                            _part = new byte[ms.Length - ms.Position];

                        await ms.ReadAsync(_part, 0, _part.Length);

                        _fileRequest = new FileRequest { FileName = file.Name, FileBytes = Google.Protobuf.UnsafeByteOperations.UnsafeWrap(_part) };
                        await call.RequestStream.WriteAsync(_fileRequest);
                        _fileRequest = null; 
                        
                    }
                }
                await call.RequestStream.CompleteAsync();
                var response = await call;
                var status = response.Status;
            }
            catch(Exception ex)
            {
                ShowMessage(ex.Message, Severity.Error);
            }
        }
    }

Method of getting the file from the server (download). Running on the server. It works very slowly. Almost does not consume RAM.

private const int _maxSize = 3 * 1024 * 1024;
        private byte[] _part = new byte[_maxSize];
        public override async Task DownloadFile(FilesInfoRequest request, IServerStreamWriter<FileRequest> responseStream, ServerCallContext context)
        {
            using (FileStream fstream = new FileStream(request.FilePath,FileMode.Open))
            {
                while (fstream.Length - fstream.Position > 0)
                {
                    if (fstream.Length - fstream.Position <= _maxSize)
                        _part = new byte[fstream.Length - fstream.Position];

                    await fstream.ReadAsync(_part, 0, _part.Length);

                    await responseStream.WriteAsync(new FileRequest
                    {
                        FileName = fstream.Name,
                        FileBytes = UnsafeByteOperations.UnsafeWrap(_part)
                    });

                }

                   
            }
}

What’s going wrong?

[JamesNK]

New docs that discuss file uploading with gRPC - https://docs.microsoft.com/en-us/aspnet/core/grpc/performance?view=aspnetcore-6.0#grpc-services-and-large-binary-payloads

[JamesNK]

rpc UploadFile(stream FileRequest) returns (StatusRequest);

I’m surprised this doesn’t error. gRPC-Web in Blazor WebAssembly doesn’t support client streaming. If it does work, then the client must be buffering all data before sending it. That would explain why you have high memory usage.

I’m not sure about the download slowness. Is this between apps on the same computer, or is there latency involved?